How Routing will be done in between RIPv1 & RIPv2 Routing Protocols

Interoperating RIPV1 & RIPV2 by Anuj Tyagi

Topology is shown below:

R1 - RIP V1 protocol

R2 - RIP V2 protocol

R3 – S0/0 in RIP v1 and S0/1 in RIP v2.

Now, After configuring R3 s0/0 in version 1 and S0/1 in version 2 .

Guess !! What should router show in

#show running-config

Where is RIP version 1 gone ???

There are two important things to look :

• As you enable Rip version 2 on router, it will add version 1 networks to version2 and Rip version1 will get disabled. Reason ? We can’t Run both version RIP version 1 & 2 on same router i.e. If we would like to use version 1 on router for any interface to make neighborship , version 2 should be disabled .
• Routers summarize it’s network routes to it’s Classful boundary. Eg. From above router RIP configuration, we are assigning 2.2.2.0/24 & 1.1.1.0/24 networks but Router summarizing them and send them as 2.0.0.0/8 & 1.0.0.0/8 .

Now, Looking at Routing-table of Routers.

For R1: As router R1 sending routes through RIP version1, it will not make neighborship or receive any updates by default.

For R2& R3:

R3 (version2) not getting updates from R1(version1) for 192.168.1.0 network.

Reason is that simple,

By default, RIP v1 & v2 can interoperate when :

• RIPv1 routers will sent only version1 packets .
• RIPv1 routers will receive both version1 and version2 updates.
• RIPv2 routers will send and receive only version2 updates.

Look at the below routing table of Router R2(version2). It’s getting 1.0.0.0/8 network updates .

So, it’s common to get successful PING from R2 to 1.1.1.2/8.

Reason ?

• 1.1.1.2/8 network is routed through Router RIP version 2. But even if R2 routing table shows 1.0.0.0/8 network in it’s routing table still it will not be able to get any PING REPLY from 1.1.1.2/8.

And if we try to PING from Router R1.

Getting successful PING REPLY from 1.1.1.2/8 is obvious as it is connected directly and doesn’t need any routing updates while R1 can’t able to reach 2.2.2.1/8 as it is not getting VERSION2 updates.

As we know, 1.1.1.1/8 is part of Router R1 which is using Rip version 1.

So, in order to make communication successful we need to make some additional configurations.

Now, question might come in some inquisitive minds why not to just configure RIP v2 on R1. That’s simple but here we want to make communication of RIP v1 with RIPv2.

So, in order to share R1 and R3 to share their routing tables

Either we can use

# ip rip send version2 on s0/0 interface of R1

to send R1 routing updates as version2 but this will not change version of RIP on router R1.

Or

We can configure Router R3 on int s0/0 to be able to receive RIP version1 updates from Router R1.

Now, behind the scenes magic will happen .

Just look at the Routing Table of Router R3 now :

.

Now, R3 and sharing their updates .

Try to ping f0/0 interface from R3, successful reply.

Now try to ping R3, R2 from R1 :

But we have not used # ip rip receive version 1 on R2 still it is getting updates from Router R3 without using # ip rip send version 1 on int s0/1 of R3.

Conclusion :

• We can’t configure both RIP version 1 &2 on a router at same time. By default, it will run version 1 but when we enable version2, version 1 will get disable automatically.
• By default, RIP version 1 will send only version 1 updates but can send both version 1&2 updates, But RIP version 2 will only send and receive version 2 updates.
• To enable RIP version 1 to send version 2 updates , we need to configure

(config-int)#ip rip send version 2

on interface .

• To enable RIP version 2 to receive both version 1&2 updates . we configure:

(config-int)#ip rip receive version 1 2

• Considering the same topology in this document, as we config #ip rip send/receive on R1& R3 interface, R2 will get R1(version 1)updates from R3 without configuring any special configuration (#ip rip send/receive version x) except Router RIP on R3 s0/1 and R2 s0/0.